Katie CouricHer GMA HostingPisses Off 'GMA' Staffers

4/2/2012 11:35 AM PDT

Katie Couric's debut as a fill-in host this week on "Good Morning America" has pissed off some of the GMA staff, who feel it's a slap in the face to vacationing co-host Robin Roberts.

GMA is breathing down the neck of "Today" and could overtake it in the ratings this week, breaking years of NBC morning show dominance. Katie's week-long stint -- along with the fact that millions of people have their TV sets tuned to ABC because of "Dancing with the Stars" -- could put it over the top.

Our GMA sources tell us it's disgusting that honchos chose the week that Robin was on vacation to put Katie on the show. They note Robin has been co-hosting GMA since 2005 and is a big reason the show is doing so well.

As one insider put it, "They should have put Katie on when George was on vacation."

And the contingent of GMA staffers who are pissed off is large -- because Robin is well-liked. And, sources tells us, although Robin is unhappy with the Katie move, she has not badmouthed anyone.

As for Katie, ABC sources say she had nothing to do with the decision to fill in and she was very conscious today that she was a "visitor on the set."